This project is a follow-up to a previous survey carried out by the NIDR in April 1980 in four areas of Illinois that have fluorides naturally occurring in their drinking water supplies at concentrations of approximately one, two, three and four times that recommended as optimal for those areas. The same communities were revisited to examine children in two of the same age groups (8-10 and 13-15 years) that were evaluated in 1980. Study participants in the 8-to-10 year age group comprised all children of those ages who received parental consent to participate and whose residence histories indicated that they had resided continuously since birth in their respective communities. The 13-to-15 year old group comprised only those children who were examined as 8-to-10 year olds in 1980. Examinations were conducted in April 1985 to assess the prevalence of dental caries and dental fluorosis in both age groups. In addition, the prevalence of gingivitis and dental calculus was assessed in all children in the 13-to-15 year age group.